Blood and bone-marrow lysozyme in neutropenia: an attempt towards pathogenetic classification

Vitamin B12 deficiency from the perspective of a practicing hematologist

B₁₂ deficiency is the leading cause of megaloblastic anemia, and although more common in the elderly, can occur at any age. Clinical disease caused by B₁₂ deficiency usually connotes severe deficiency, resulting from a failure of the gastric or ileal phase of physiological B₁₂ absorption, best exemplified by the autoimmune disease pernicious anemia. There are many other causes of B₁₂ deficiency, which range from severe to mild. Mild deficiency usually results from failure to render food B₁₂ bioavailable or from dietary inadequacy. Although rarely resulting in megaloblastic anemia, mild deficiency may be associated with neurocognitive and other consequences. B₁₂ deficiency is best diagnosed using a combination of tests because none alone is completely reliable. The features of B₁₂ deficiency are variable and may be atypical. Timely diagnosis is important, and treatment is gratifying. Failure to diagnose B₁₂ deficiency can have dire consequences, usually neurological. This review is written from the perspective of a practicing hematologist.

Mutations of the Listeria monocytogenes peptidoglycan N-deacetylase and O-acetylase result in enhanced lysozyme sensitivity, bacteriolysis, and hyperinduction of innate immune pathways

Listeria monocytogenes is a Gram-positive intracellular pathogen that is naturally resistant to lysozyme. Recently, it was shown that peptidoglycan modification by N-deacetylation or O-acetylation confers resistance to lysozyme in various Gram-positive bacteria, including L. monocytogenes. L. monocytogenes peptidoglycan is deacetylated by the action of N-acetylglucosamine deacetylase (Pgd) and acetylated by O-acetylmuramic acid transferase (Oat). We characterized Pgd(-), Oat(-), and double mutants to determine the specific role of L. monocytogenes peptidoglycan acetylation in conferring lysozyme sensitivity during infection of macrophages and mice. Pgd(-) and Pgd(-) Oat(-) double mutants were attenuated approximately 2 and 3.5 logs, respectively, in vivo. In bone-marrow derived macrophages, the mutants demonstrated intracellular growth defects and increased induction of cytokine transcriptional responses that emanated from a phagosome and the cytosol. Lysozyme-sensitive mutants underwent bacteriolysis in the macrophage cytosol, resulting in AIM2-dependent pyroptosis. Each of the in vitro phenotypes was rescued upon infection of LysM(-) macrophages. The addition of extracellular lysozyme to LysM(-) macrophages restored cytokine induction, host cell death, and L. monocytogenes growth inhibition. This surprising observation suggests that extracellular lysozyme can access the macrophage cytosol and act on intracellular lysozyme-sensitive bacteria.

Effects of magnetic resonance imaging on polymorphonuclear neutrophil functions

RATIONALE AND OBJECTIVES

Limited research has been performed on the effects of magnetic resonance (MR) imaging on the immune system. To our knowledge, there are no reported studies of MR imaging effects on the polymorphonuclear neutrophil (PMN) system. Therefore, we evaluated the influence of MR imaging exposure on PMNs.

METHODS

In vivo and in vitro studies were performed on 36 patients undergoing MR imaging. The following were estimated in blood samples: leukocyte and PMN count, PMN phagocytosis and bactericidal capacity, percentage of cells with expression of surface receptor for the Fc fragment of immunoglobulin G (IgG), PMN superoxide, hydrogen peroxide production, and plasma lysozyme activity. Another sample of patients was used to eliminate temperature as an influence on changes in PMN functions.

RESULTS

Both in vitro and in vivo MR imaging led to a decrease in PMNs and an increase in PMN phagocytosis, bactericidal capacity, hydrogen peroxide production, and percentage of cells with expression of surface receptor for Fc IgG. Superoxide anion production did not change significantly. Elevated temperature, stress, and anxiety were excluded as influences on our results.

CONCLUSION

The PMN system is affected seriously by MR imaging.

[Studies of lysozyme activity in serum, urine and blood smears from patients with haematological diseases]

Lysozyme activity was studied in blood smears, serum, and urine of patients suffering from leukaemia or other haematological diseases. Increased enzyme activity was found in myelocytic, myelomonocytic and monocytic leukaemia and equally in secondary granulocytosis and polycythaemia vera. Reduced rates were found in lymphocytie leukaemia, malignant lymphoma with bone marrow involvement, and myelophthisic conditions. A rise in urinary lysozyme occurred when the serum level exceeded 50 microgram/ml. Abundant activities were found in myelomonocytic and monocytic leukaemias. Using the bacteriolytic method in blood smears, no enzyme activity was demonstrated in cells of acute or chronic lymphocytic leukaemia, in monocytic leukaemia however, almost all cells show strong reaction. In acute myelocytic or myelomonocytic leukaemia, the portion of positive cells changes from case to case depending on the degree of cell differentiation and maturation. In chronic myelocytic leukaemia there was no difference as compared to enzyme activity of myelocytes in bone marrow of control cases. Thus the bacteriolytic demonstration of lysozyme in blood smears may additionally contribute to distinction of different types of blastic leukaemias, and serum lysozyme also may allow more reliable insight into granulocytic and monocytic myelopoiesis than morphologic studies of blood or bone marrow smears can do, e.g. in agranulocytosis and pancytopenia.

Assessment of the value of prednisone test in differential diagnosis of neutropenic state

The prednisone test revealed normal bone marrow reserve of neutrophils (BMR) in subjects with innocent neutropenias e.g. neutropenias not associated with any other disturbances in haemopoiesis or with increased incidence of infections, assumed to be an individual anomaly of the subject. On the other hand, diminution or absence of MBR in chronic hypoplastic neutropenias, transient post-chemotherapeutic neutropenias and neutropenias with increased destruction of neutrophils were observed. The magnitude of that diminution was not dependent of the cause of neutropenia. It is suggested, that the prednisone test (and probably tests with other BMR mobilizing agents) may serve as screening tests for exclusion (or confirmation) of relative granulopoietic insufficiency as the cause of neutropenia. Only after confirmation of reduced BMR another explanations of neutropenia should be sought using other method as muramidase level, adrenaline test or granulocyte kinetics with DF32P, 3HDFP, or 51Cr.

Neutrophil kinetics in corticosteroid induced neutrophilia measured by plasma lysozyme

A single dose of prednisone (2 mg/kg orally) resulted in a mean rise in neutrophil counts to 2.3 (range 1.5-3.6) and a mean decrease in plasma lysozyme to 0.73 (range 0.50-0.87) times the value before the steroid was given in 10 haematologically normal persons. There was no change in the intraneutrophilic lysozyme activity. It is concluded that the decrease in plasma lysozyme is compatible with a reduction in the egress of neutrophils to the tissues and a decrease in the neutrophil turnover rate.